In the continuous casting of steel it was found that improved results are obtained by providing on the upper surface of the molten steel a protective layer of synthetic slag. The term "slag" and the term "flux" have often been used interchangeably in this context for fritted or predominantly fritted mold powders for continuous casting purposes. In the present context, a particulate slagging composition will be defined as encompassing all types of materials used to protect and lubricate steel during the continuous casting process. In the present context, mold powders are essentially raw materials which have not been vitrified to any appreciable extent.
The relevant art is noted to include U.S. Pat. No. 3,649,249 which disclosed a synthetic slag forming composition for use in a continuous casting process. A fluorine containing flux composition in the form of frit particles has also been disclosed in U.S. Pat. No. 3,899,324. The presence of fluorine was long recognized to have an undesirable effect on the linings of smelters. A chemical attack generally manifests itself by the dissolution of the brick lining which makes repair work necessary. Additionally, volatilized fluorides need to be recovered due to environmental considerations. A solution to the problem associated with the inclusion of fluorine in raw materials of frit compositions was presented in U.S. Pat. No. 4,092,159. The invention entailed smelting vitrifiable raw materials for the preparation of a frit containing a limited amount of fluorine and blending the frit with a fluorine providing material in the form of discreet unvitrified particles.
In U.S. Pat. No. 4,204,864 there was disclosed a particulate slagging composition useful in the continuous casting of steel which is characterized in the absence of lithium therefrom.
It is an object of the invention to provide a particulate slagging composition suitable for use in the continuous casting of steel. Further, it is an object of the invention to provide a particulate slagging composition which is fluorine free. It is also an object of the invention to provide a particulate slagging composition which due to its rheology and chemistry is an excellent lubricant in the context of the continuous casting of steel.